Earhealth monitoring system and method IV

ABSTRACT

A system for monitoring sound pressure levels at the ear includes an ambient sound microphone (ASM) for receiving ambient sounds and an ear canal microphone (ECM) for producing audio signals as a function of ambient sound received at the ambient sound microphone and a sound signal received from an associated personal audio device. A logic circuit is operatively associated with the ASM and ECM calculates a total SPL_Dose experienced by the ear at a time t. The total SPL_Dose is calculated by determining SPL_Dose for periods Δt as measured at the ECM. The logic circuit may select an action parameter in response to the Total SPL_Dose.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.11/931,252, filed Oct. 31, 2007, which is a Continuation-In-Part of U.S.patent application Ser. No. 11/757,152 filed on 1 Jun. 2007, thedisclosure of which is incorporated herein by reference in its entirety,which in turn claims priority from U.S. Provisional Application No.60/803,708 filed on 1 Jun. 2006.

FIELD OF THE INVENTION

The present invention relates to a device that monitors acoustic energydirected to an ear, and more particularly, though not exclusively, to anearpiece that monitors acoustic sound pressure level dose received by auser's ear.

BACKGROUND OF THE INVENTION

With the advent of an industrial society, people are exposed to noisepollution at greater and greater levels; both from background, such asstreet traffic, airplanes, construction sites and intentional exposureto high sound levels such as cell phones, MP3 players, and rockconcerts. Studies show that ear damage, leading to permanent hearingimpairment is not only increasing in the general population, butincreasing at a significantly faster rate in younger populations.

The potential for hearing damage is a function of both the level and theduration of exposure to the sound stimulus. Safe listening durations atvarious loudness levels are known, and can be calculated by averagingaudio output levels over time to yield a time-weighted average. Standarddamage-risk guidelines published by OSHA, NIOSH or other agencies areknown. This calculation can be even further improved by or accountingfor aspects of the playback scenario, specifically the characteristicsof the sound source and their proximity to the listener's ear.

Studies have also indicated that hearing damage is a cumulativephenomenon. Although hearing damage due to industrial or backgroundnoise exposure is more thoroughly understood, the risk of exposing one'sself to excessive noise, especially with the use of headphones has alsobeen recently studied. Protecting the ear from ambient noise isprimarily done with the use of static earplugs that attempt to shieldthe inner ear from excessively high decibel noise. Background noisecanceling earphones such as those produced by Bose and others, attemptto protect the ear from excessive ambient noise by producing a counternoise wave to cancel out the ambient noise at the ear. These prior artdevices have been less than satisfactory because they do not completelyprevent high decibel noise from reaching the ear, and do not account forthe duration of exposure to harmful sounds at the ear.

It is also known from the prior art to provide active noise reduction atthe ear to protect the ear from exposure to loud noises as disclosed inU.S. patent Application No. US2005/0254665. The art actively attenuatingnoise reaching the inner ear utilizing a control; a connection with anearpiece and attenuating the noise to the ear. However, there is nomonitoring of the noise over time to account for the cumulative effect.Furthermore, there is no accounting for any restorative effects withinthe ear for sound level exposures, which are sufficiently low to allowrecovery, rather than destruction.

Dosimeters, such as that described in U.S. published Application No.US2005/0254667 are known. The device periodically measures prior soundlevel in the ambient environment. However, the device does not take intoaccount the cumulative effect of the noise over multiple incidences ofexposure (e.g., one day to the next) or the effect of any restorativeperiod. Furthermore, no remedial action is automatically taken as aresult of the readings.

It is also known from the prior art that headphones for consumerelectronics have been provided with a predetermined maximum output levelin an attempt to prevent ear damage. This approach is ineffective as itdoes not take into account listening duration and the calculation ofrisk for auditory injury. Other headphones are maximum-limited toproduce levels that can still result in significant overexposure givenenough time, or limit the user to levels, which may not be sufficient toachieve an adequate short term listening level. In the latter case,consumer acceptance for the protective gear could be severely limitedand a product would fail to survive in a competitive market andtherefore be of no use.

Another alternative known in the art is to reduce the headphone outputlevels by increasing earphone impedance via an accessory placed betweenthe media player and the earphones. The limitation of this approach isthat it gives no consideration to the duration of exposure, and againeither the user's chosen listening level cannot be achieved because themaximum level is too limited, or the level is sufficient to allow theuser access to high enough sound levels, but risk overexposure due topotential duration of use.

It is known from U.S. Publication No. 2007/0129828 to provide automatedcontrol of audio volume parameters in order to protect hearing. A methodof operating a media player includes the step of playing back audiomedia and refining a maximum volume parameter for the playing of themedia by the media player. The refining is based at least in part on theplayback of audio media during a time period existing prior to theexecution of refining the maximum volume allowed. The refinement isintended to minimize harm to the user's hearing.

Applicants cannot confirm that such an approach has been commercialized.However, even if commercialized, it suffers from the shortcomings thatthe refinement is based on a theoretical noise volume delivered to theear as a function of the output signal of the device and parameters ofthe earpiece connected to the device and is based upon a credit systembased on volume. There is no measurement of the actual noise deliveredto the ear. Furthermore, the calculation does not take into account theambient noise of the device user or the noise reduction rate of theearpiece relative to the ambient noise. In other words, the actualvolume level to which the ear is exposed is not taken into account.Accordingly, a severe miscalculation of the actual ear expose, andresulting ear harm, may exist as a result of use of this related artmethod. Additionally the credit system is not described in detailsufficient for one of ordinary skill to construct the device. Forexample U.S. Publication No. 2007/0129828 refers to Cal-OSHA profiles,and states in the same paragraph that Cal-OSHA appear to be rudimentaryand does not deal with exposure “in a sophisticated way with varyingexposure over time” and does not “ . . . account for recovery.” However,U.S. Publication No. 2007/0129828 states in one example “ . . . themaximum allowed volume is determined based upon determined credits withreference to a profile such as profiles provided by . . . (Cal-OSHA) . .. ” However, U.S. Publication No. 2007/0129828, stated that Cal-OSHAdoesn't take into effect recovery, and additionally fails to refer toany detailed recovery calculation.

Accordingly, a system that overcomes the shortcomings in the related artwould be useful.

BRIEF SUMMARY OF THE INVENTION

A system for monitoring sound pressure levels at the ear includes anambient sound microphone (ASM) for receiving ambient sounds and an earcanal microphone (ECM) for producing audio signals as a function ofambient sound received at the ambient sound microphone and sound signalreceived from an associated personal audio device. A logic circuit isoperatively associated with the ASM and ECM calculates a total SPL_Doseexperienced by the ear at a time t.

In one exemplary embodiment the total SPL_Dose is calculated bydetermining SPL_Dose for periods Δt as measured at the ECM. The logiccircuit may then select an action parameter in response to the TotalSPL_Dose.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the system for measuring and determiningexposure to sound over time at the ear constructed in accordance with afirst exemplary embodiment of the invention.

FIG. 2 is a block diagram of the system in accordance with at least oneexemplary embodiment of the invention in situ in the ear;

FIG. 3 is a flow chart for calculating listening fatigue in accordancewith at least one embodiment of the invention by measuring a quantity(e.g., the sound pressure level) over time as received at the ear;

FIG. 4 is a flow chart for determining a weighted ear canal soundpressure level in accordance with another exemplary embodiment of theinvention;

FIG. 5 is a flow chart for determining a personalized recovery timeconstant in accordance with another exemplary embodiment of theinvention;

FIG. 6 is a flow chart for determining an update epoch in accordancewith at least one exemplary embodiment of the invention;

FIG. 7 is a flow chart for determining an update epoch in accordancewith yet another exemplary embodiment of the invention;

FIG. 8 illustrates the general configuration and terminology inaccordance with descriptions of exemplary embodiments;

FIGS. 9A-9C illustrates an example of a temporal acoustic signal and itsconversion into a spectral acoustic signature;

FIG. 10 illustrates a generalized version of an earpiece and someassociated parts in an ear canal;

FIG. 11 illustrates an earpiece according to at least one exemplaryembodiment;

FIG. 12 illustrates a self-contained version of an earpiece according toat least one exemplary embodiment;

FIG. 13 illustrates an earpiece where parts are not contained in theearpiece directly according to at least one exemplary embodiment;

FIG. 14A illustrates a general configuration of some elements of anearpiece according to at least one exemplary embodiment;

FIG. 14B illustrates a flow diagram of a method for SPL_Dose calculationaccording to at least one exemplary embodiment;

FIGS. 15A to 15N illustrate various non-limiting examples of earpiecesthat can use methods according to at least one exemplary embodiment;

FIG. 16 illustrates a line diagram of an earpiece (e.g., earbud) thatcan use methods according to at least one exemplary embodiment; and

FIG. 17 illustrates the earpiece of FIG. 16 fitted in an ear.

DETAILED DESCRIPTION OF THE INVENTION

The following description of at least one exemplary embodiment is merelyillustrative in nature and is in no way intended to limit the invention,its application, or uses.

Processes, techniques, apparatus, and materials as known by one ofordinary skill in the relevant art may not be discussed in detail butare intended to be part of the enabling description where appropriate,for example the fabrication and use of transducers. Additionally in atleast one exemplary embodiment the sampling rate of the transducers canbe varied to pick up pulses of sound, for example less than 50milliseconds.

In all of the examples illustrated and discussed herein, any specificvalues, for example the sound pressure level change, should beinterpreted to be illustrative only and non-limiting. Thus, otherexamples of the exemplary embodiments could have different values.

Note that similar reference numerals and letters refer to similar itemsin the following figures, and thus once an item is defined in onefigure, it may not be discussed for following figures.

Note that herein when referring to correcting or preventing an error ordamage (e.g., hearing damage), a reduction of the damage or error and/ora correction of the damage or error are intended.

At least one exemplary embodiment of the invention is directed tomeasuring and determining the exposure of the ear to sound over time.Reference is made to FIG. 1 in which a system, generally indicated as100, is constructed in accordance with at least one exemplary embodimentof the invention. System 100 includes an audio input device 113 forreceiving sound at the ear. As will be discussed below, audio inputdevice 113 can include an analog audio input 11, 23 and a digital audioinput 19. In at least one exemplary embodiment, audio input device 113receives audio input from at least one of three sources, namely; ambientnoise around the ear, direct input noise such as a MP3 player or otherdevice which can produce a digital audio input at digital audio input19, and noise as detected within the ear canal 31 (FIG. 2). The audioinput device 113 outputs an audio signal corresponding to the receivedsound. Analog output signals from analog audio inputs 11, 23 areconverted to a digital signal by an analog-to-digital (A/D) converter118 so that digital sound signals are input into an input level detector120.

Input level detector 120 determines the sound pressure level of thesound received at audio input device 113. Input level detector 120outputs a sound pressure level (SPL) signal, which is input to aminimum-level threshold detector 122. Minimum level threshold detector122 determines whether or not the sound pressure level as detected byinput level detector 120 exceeds a minimum level threshold. As will bediscussed below, the minimum level threshold can be the permissiblesound level PSL (e.g., effective quiet level) of the individual, or somepredetermined level substantially corresponding to a level, which is eardamage neutral over time, or a level of interest, such as 80 dB, becauseof its effect on the ear. Therefore, if the minimum level threshold isdetected as being exceeded, a signal indicating a sound pressure levelin excess of the minimum level threshold is output to a start timer 124,which triggers a digital timer system 126 to begin a clock. Conversely,if the input sound pressure level is detected as being below the minimumthreshold, a signal indicating the sound pressure level is below theminimum level threshold is output to a start timer 124, which triggers adigital timer system 126 to begin a clock of a restorative period. Ifthe sound pressure level is at the minimum threshold (within a margin oferror), no clock needs to be started because this is neutral to thedesired effect. In a preferred embodiment, the clock signal is changedwith every significant (more than 1 dB by way of example) change insound pressure level to get an accurate profile of sound exposure overtime.

Once the sound pressure level as detected at input level detector 120decreases to or is below the minimum threshold level, a stop timersignal is output from stop timer 128 to digital timer system 126 to stopthe clock corresponding to exposure to the excessively intense level.Digital timer system 126 outputs a clock value corresponding to the timeperiod at which the minimum level threshold was not met, or in thepreferred embodiment, for each period corresponding to a discrete levelchange.

A data memory or learning history database 127 receives the clock valuefrom digital timer system 126 as well as the actual input level detectedat input level detector 120 and determines a listening history or soundpressure level exposure history. The sound pressure level exposurehistory is a record of the user's exposure to sound pressure levels overtime. Because the effect of exposure is cumulative, it is important thatthe exposure history be maintained. The listening history, as will bediscussed below, can include real ear level data, listening durationdata, time between listening sessions, absolute time, sound pressurelevel dose (SPL_Dose) data, including any restorative sound level,number of acoustic transients and crest factor and other data.

The sound pressure level exposure history or listening history includesboth the listening habits history and the environmental or ambient noiseexposure history. The environmental noise exposure history is theexposure of a user to environmental noise over time as a result of theauditory stimuli inherent to the environment where the user is present.This can be highway traffic, construction site, even the restorativeeffect of the quiet sound pressure levels, e.g., those typicallyencountered in a library whereas, the listening habits history isassociated for the purposes for this disclosure with user-directedauditory stimuli such as music, words, other noises, which a userintentionally encounters for a purpose such as communication, learning,and enjoyment. Therefore, database 127, as will be discussed below,stores the cumulative SPL exposure.

It should be noted that in at least one exemplary embodiment, minimumlevel threshold detector 122 also starts the timer 124 when the soundpressure level is below the predetermined level. In this way, therestorative effect of sound levels below PSL (e.g., effective quietnoise) is accumulated for determining overall exposure damage potential.

In effect, the only time that digital timer system 126 is not running iswhen the detected sound pressure level signal is at the minimum levelthreshold. A listening fatigue calculator 130 receives the input levelsignal from input level detector 120 and data from the data memorylistening history 127, and determines whether or not listening fatigueor hearing damage is likely to occur as a result of further exposure.Hearing damage is the injury to the hearing mechanism includingconductive and sensorineural decrement in hearing threshold levels. Itcan be either temporary or permanent so long as it is a result of thenoise exposure that is above PSL (e.g., Effective Quiet). In otherwords, listening fatigue calculator 130 will output a signal when athreshold sound exposure, determined as a function of exposure time andsound pressure level, as will be discussed in greater detail below, isachieved. At that point, a listening fatigue signal is output.

It should be noted that in an alternative embodiment, system 100 canmake use of an ambient noise detection/cancellation system 142 as knownin the art. These systems produce signals, which cancel sound pressurelevels at certain frequencies and/or certain levels to reduce the effectof undesired noise, whether environmental noise or user directed noise.It will have some effect in elongating the permissible exposure time bynegating the sound pressure level detected by input level detector 120.

In at least one exemplary embodiment, the signal from the listeningfatigue calculator is utilized to prevent damage and encourages someaction by the user when exposure levels are near damaging levels.Therefore, in one non-limiting example, a listening fatigue display 140is provided for receiving the signal from the listening fatiguecalculator and displaying to the user a prompt to discontinue exposureto the sound level from the damaging sound source or audio source.

In another non-limiting example, the signal from the listening fatiguecalculator is output to an audio warning source 132, which outputs anoutput audio warning to the user notifying the user that exposure to thesound source has reached critical levels.

In at least one exemplary, but non-limiting, embodiment, as will bediscussed below, system 100 includes an output acoustical transducer 25to provide an audio signal to the ear. Output acoustical transducer 25operates under the control of a digital signal processor (DSP) 134.Digital signal processor 134 receives a digital audio signal from inputlevel detector 120, which acts as a pass through for the digitizedsignals from audio input device 113. Digital signal processor 134 passesthe sound signals through to a digital to analog (D/A) converter 136 todrive acoustical transducers 25 to recreate the sound received at audioinput device 113 inside the ear canal 31 in at least one exemplaryembodiment of the invention as shown in FIG. 2. With such an exemplaryembodiment, audio warning source 132 provides an output to digital soundprocessor 134 causing output acoustical transducer 25 to output awarning sound inside the ear of the user.

Additionally, in at least one further exemplary embodiment, listeningfatigue calculator 130 outputs a listening fatigue signal to digitalprocessor 134 which causes digital signal processor 134 to attenuate thesound signal prior to output to acoustical transducer 25 to reduce thesignal output level by any of the linear gain reduction, dynamic rangereduction, a combination of both, or a complete shutdown of transducer25. Attenuation would be at least to the level, if not below, the PSL(e.g., effective quiet level) to allow for ear recovery prior to damage.

It should be noted, that because personal hearing threshold anddiscomfort levels can change from person to person, and because both ofthe time intervals are a function of many variables, in a non-limitingexample, to provide a dynamic ever-changing response, system 100operates under software control. The configuration of the digital soundprocessor 134, listening fatigue calculator 130, the minimum levelthreshold detector 122, and the input level detector 120 are operatedunder software control.

In an exemplary embodiment of the invention, the control programs arestored in a program memory 148 for operating the firmware/hardwareidentified above. Furthermore, the program stored within memory 148 canbe personalized as a result of testing of the user's ear, or by othermodeling methods, in which system 100 includes a software interface 144for receiving online or remote source updates and configurations. Thesoftware interface 144 communicates with a data port interface 146within system 100, which allows the input of software updates to programmemory 148. The updates can be transmitted across a distributedcommunications network, such as the Internet, where the updates take theform of online updates and configurations 143.

It should be noted that there is multiple functionality distributedacross system 100. In at least one exemplary embodiment, at least audioinput device 113 and acoustical transducer 25 are formed as an earpiece,which extends into the outer ear canal so that the processing of signalspertains to sound received at the ear. However, it is well within thescope of at least one exemplary embodiment of the invention to providesubstantially all of the functionality in an earpiece so that system 100is a “smart device.”

Also note that when referring to measurements in decibels (dB) one isreferring to a logarithmic ratio. For example dB is defined as:

$\begin{matrix}{{S\; P\; L} = {{\beta({dB})} = {{10\;\log\frac{I}{I_{0}}} = {10\mspace{11mu}\log\frac{\Delta\; P^{2}}{\Delta\; P_{0}^{2}}}}}} & (1)\end{matrix}$

Where I is the intensity measured, I₀ is a reference intensity,I₀=10⁻¹²W/m², and P₀ is a reference pressure, ΔP₀=20 micropascals, andwhere ΔP is the root mean squared pressure amplitude in a measuredpressure wave (e.g., using a transducer). Thus, the sound pressure level(SPL) can be measured in dB.

Alternatively, one can use the above equation and solve for measuredpressures instead. For example:ΔP(t)=10^((SPL(t)/20.0)) ΔP ₀  (2)

In the discussion of formulas herein we refer to SPL as a non-limitingexample and one of ordinary skill in the arts could re-derive theequations in terms of measured pressures, ΔP, both are intended to liewithin the scope of at least one exemplary embodiment. Reference is nowmade to FIG. 2 in which system 100 in which the transducerconfiguration, that portion of system 100, which converts sound pressurelevel variations into electrical voltages or vice versa is shown. Inthis embodiment, acoustic transducers include microphones as an inputand loudspeakers as an acoustical output.

FIG. 2 depicts the electro acoustical assembly 13 (also referred toherein as an in-the-ear acoustic assembly 13 or earpiece 13), as itwould typically be placed in the ear canal 31 of ear 17 of user 35. Theassembly is designed to be inserted into the user's ear canal 31, and toform an acoustic seal with the walls 29 of the ear canal 31 at alocation 27, between the entrance 15 to the ear canal and the tympanicmembrane or eardrum 33. Such a seal is typically achieved by means of asoft and compliant housing of assembly 13. A seal is critical to theperformance of the system in that it creates a closed cavity in earcanal 31 of approximately 0.5 cc in a non-limiting example between thein-ear assembly 13 and the ear's tympanic membrane 33.

As a result of this seal, the output transducer (speaker) 25 is able togenerate a full range bass response when reproducing sounds for thesystem user. This seal also serves to significantly reduce the soundpressure level at the user's eardrum 33 resulting from the free/diffusesound field at the entrance 15 to the ear canal 31. This seal is alsothe basis for the sound isolating performance of the electroacousticassembly 13. Located adjacent to speaker 25, is an ear canal microphone(ECM) 23, which is also acoustically coupled to closed cavity 31. One ofits functions is that of measuring the sound pressure level in cavity 31as a part of testing the hearing sensitivity of the user as well asconfirming the integrity of the acoustic seal and the working conditionof itself and speaker 25. Audio input 11 (also referred to herein asambient sound microphone (ASM) 11) is housed in assembly 13 and monitorssound pressure at the entrance 15 to the occluded ear canal. Thetransducers can receive or transmit audio signals to an ASIC 21 thatundertakes at least a portion of the audio signal processing describedabove and provides a transceiver for audio via the wired or wirelesscommunication path 119.

In the above description the operation of system 100 is driven by soundpressure level, i.e. sound levels are monitored for time periods orepochs during which the sound pressure level does not equal the minimumlevel threshold or is constant. However, as will be discussed inconnection with the next exemplary embodiments of the invention, system100 can also operate utilizing fixed or variable sampling epochsdetermined as a function of one or more of time and changes in soundpressure level, sound pressure level dosage, weighting functions to thesound pressure level, and restorative properties of the ear.

Reference is now made to FIG. 3 in which a flow chart for monitoring thesound pressure level dose at various sample times n is provided. Theprocess is started in a step 302. An input audio signal is generated ina step 304 at either the ear canal microphone (ECM) 23 or the ambientsound microphone (ASM) 11. Changes in SPL_Dose resulting from durationof exposure time is a function of the sound pressure level, therefore,the epoch or time period used to measure ear exposure or, moreimportantly, the time-period for sampling sound pressure level isdetermined in a step 305. The update epoch is used in the SPL_Dosefunction determination as well as to effect the integration period forthe sound pressure level calculation that, as will be discussed below,is used to calculate the weighted ear canal sound pressure level.

Reference is now made to FIGS. 6 and 7. In FIG. 6, a method is definedto change the update epoch as a function of the weighted ear canal soundpressure level, which will be discussed in greater detail below. System100 is capable of determining when earpiece 13 is in a charger orcommunication cradle (i.e., not in use in the ear of the user). In astep 684, a predetermined standard is provided for the update epoch, 60seconds in this example. In step 688, the update epoch is set as thein-cradle update epoch. The in-cradle state is detected in step 686. Ifit is determined in a step 690 earpiece 13 (also referred to herein asearphone device 13) is in a charger or cradle mode, then the updateepoch is set as the in-cradle epoch; in the step 688.

However, if in step 690 it is determined that the earphone device 13 isin use, in other words “not in the cradle”, then, by default, an audiosignal is input to earpiece 13 in step 692. In step 693, an ear canalsound pressure level is estimated as a function of the audio input atstep 692. The current (n) ear canal sound pressure level estimate isstored as a delay level in a step 698. An audio input is determined at alater time when step 692 is repeated so that a second in-time ear canalsound pressure level estimate is determined.

In a step 600, the delayed (n−1) or previous sound pressure level iscompared with the current (n) ear canal sound pressure level estimate tocalculate a rate of change of the sound pressure level. The change levelis calculated in units of dB per second. This process of step 692through 600 is periodically repeated.

In a step 606, it is determined whether or not the sound pressure levelchange is less than a predetermined amount (substantially 1 dB by way ofnon-limiting example) between iterations, i.e., since the last time theear canal sound pressure level is calculated. If the change is less thanthe predetermined amount, then in step 604 the update epoch isincreased. It is then determined in a step 602 whether or not the epochupdate is greater than a predefined amount D set in step 694 as amaximum update epoch such as 60 seconds in a non-limiting example. If infact, the update epoch has a value greater than the maximum update epochD then the update epoch is set at the higher value D in step 608.

If it is determined in step 606 that the sound pressure level change is,in a non-limiting example, greater than −1 dB, but less than +1 dB asdetermined in step 612, then the update epoch value is maintained in astep 610. However, if it is determined that the sound pressure levelchange is, in a non-limiting example, greater than +1 dB, then theupdate epoch value is decreased in a step 618 to obtain more frequentsampling. A minimum predetermined update epoch value such as 250microseconds is set in a step 614. If the decreased update epochdetermined in step 618 is less than, in other words an even smallerminimum time-period than the predetermined minimum update epoch E, thenthe new update epoch is set as the new minimum update epoch value insteps 616 and 622. In this way, the sample period is continuously beingadjusted as a function of the change in sound pressure level at the ear.As a result, if the noise is of a transient variety as opposed to aconstant value, the sampling interval will be changed to detect suchtransients (e.g., spikes) and can protect the ear.

Reference is now made to FIG. 7 in which a method for changing theupdate epoch is illustrated as a function of the way that the ear canalsound pressure level estimate is provided. Again, in accordance with atleast one exemplary embodiment of the invention, the update epoch isdecreased when the ear canal sound pressure level is high or increasing.

The difference between the embodiment of FIG. 7 and the embodiment ofFIG. 6 is that the update epoch is not continuously adjusted, but ismore static. If the ear canal sound pressure level is less than PSL(e.g., effective quiet, a decibel level which when the ear is exposed toover time does not damage or facilitate restoration the ear), then theupdate epoch is fixed at a predefined maximum epoch value and this isthe value used by system 100 as will be discussed in connection withFIG. 3 below. A system for monitoring sound pressure levels at the earincludes an ambient sound microphone for receiving ambient sounds and anear canal microphone for producing audio signals as a function ofambient sound received at the ambient sound microphone and sound signalreceived from an associated personal audio device. A logic circuit isoperatively associated with the ASM and calculates a Total SPL_Doseexperienced by the ear at a time t.

In one exemplary embodiment the Total SPL_Dose is calculated bydetermining estimated SPL_Dose for periods Δt. The logic circuit maythen select an action parameter in response to the Total SPL_Dose. If itis determined to be greater than a permissible (or permitted) soundlevel (PSL) (e.g., effective quiet), then the update epoch is fixed at ashorter minimum value and this is returned as the update epoch to beutilized.

In FIG. 7, specifically, as with FIG. 6, an in-cradle update epoch of 5seconds by way of non-limiting example, is stored in system 100 in astep 784. In a step 788, the initial update epoch is set as thein-cradle update epoch. A maximum update epoch time, such as 2 secondsby way of non-limiting example, is stored in a step 794. In a step 714,an initial minimum update epoch (250 microseconds in this non-limitingexample) is stored.

In a step 786 and step 790 it is determined whether or not system 100 isin a non-use state, i.e., being charged or in a cradle. If so, then theupdate epoch is set at the in-cradle update epoch. If not, then adigital audio signal is input from ear canal microphone 23 in step 792.A sound pressure level is estimated in step 795. It is then determinedwhether or not the ear canal sound pressure level is less than PSL(e.g., effective quiet) in a step 732. If the sound pressure level isless than the PSL (e.g., effective quiet) as determined in step 732,then the update epoch is set at the maximum update epoch in a step 730.If the sound pressure level is more intense than the effective quiet,then in step 716, the update epoch is set to the minimum update epoch.

Returning to FIG. 3, in a non-limiting exemplary embodiment, the updateepoch is set at 10 seconds in a step 302 utilizing either a constantpredetermined sample time, or either of the methodologies discussedabove in connection with FIGS. 6 and 7. In a step 306, the input audiosignal is sampled, held, and integrated over the duration of the epochas determined in step 308. As a result, the update epoch affects theintegration period utilized to calculate the sound pressure level doseas a function of the sound pressure level and/or as the weighted earcanal sound pressure level.

In a step 310, an earplug noise reduction rating (NRR) is stored. Thenoise reduction rating corresponds to the attenuation effect of earpiece13, or system 100, on sound as it is received at audio input 11 andoutput at the output transducer 25 or as it passes from the outer ear tothe inner ear, if any exemplary embodiment has no ambient soundmicrophone 11. In a step 311, a weighted ear canal sound pressure levelis determined, partially as a function of the earplug noise reductionrating value.

Reference is now made to FIG. 4 where a method for determining theweighted ear canal sound pressure level in accordance with at least oneexemplary embodiment of the invention is illustrated. Like numerals areutilized to indicate like structure for ease of discussion andunderstanding. Weighting is done to compensate for the manner in whichsound is perceived by the ear as a function of frequency and pressurelevel. As sounds increase in intensity, the auditory perception ofloudness of lower frequencies increases in a nonlinear fashion. Byweighting, if the level of the sound in the sound field is low, themethodology and system utilized by at least one exemplary embodiment ofthe invention reduces the low frequency and high frequency sounds tobetter replicate the sound as perceived by the ear.

Specifically, a weighting curve lookup table, such as A-weighting, actsas a virtual band-pass filter for frequencies at sound pressure levels.In a step 304, the audio signal is input. In step 410,frequency-dependent earplug noise reduction ratings are stored. Thesevalues are frequency-dependent and in most cases, set asmanufacturer-specific characteristics.

As discussed above, in a step 306, the input audio signal is shaped,buffered and integrated over the duration of each epoch. The soundpressure level of the shaped signal is then determined in a step 436. Itis determined whether or not ambient sound microphone (ASM) 11 wasutilized to determine the sound pressure level in a step 444. Ifmicrophone 11 was utilized, then the frequency-dependent earplug noisereduction rating of earpiece 13 must be accounted for to determine thesound level within the ear. Therefore, the noise reduction rating, asstored in step 310, is utilized with the sound pressure level todetermine a true sound pressure level (at step 446) as follows:SPL_(ACT)=SPL−NRR:  (3)where sound pressure SPL_(ACT) is the actual sound pressure levelreceived at the ear medial to the ECR, SPL is the sound pressure leveldetermined in step 436 and NRR is the noise reduction rating valuestored in step 410.

If the ambient sound microphone (ASM) 11 is not used to determine thesound pressure level then the sound pressure level determined in step436 is the actual sound pressure level. So that:SPL_(ACT)=SPL  (4)

It is well within the scope of at least one exemplary embodiment of theinvention to utilize the actual sound pressure level as determined sofar to determine the affect of the sound pressure level received at theear on the health of the ear. However, in at least one exemplaryembodiment, the sound pressure level is weighted to better emulate thesound as received at the ear. Therefore, in a step 412, a weightingcurve lookup table is stored within system 100. In a step 440, theweighting curve is determined as a function of the actual sound pressurelevel as calculated or determined above in steps 436, 446 utilizing aweighting curve lookup table such as the A-weighting curve. TheA-weighting curve is then applied as a filter in step 438 to the actualsound pressure level. A weighted sound pressure level valuerepresentative of a sampled time period (SPL_W(n)) is obtained to beutilized in a step 414.

The weighting curve can be determined in step 440 by applying afrequency domain multiplication of the sound pressure level vector andthe weighting curve stored in step 412. In this exemplary embodiment,the weighting curve would be appropriate for direct multiplication withthe SPL in the frequency domain (i.e., SPL(f)). In another exemplaryembodiment the weighted SPL can be expressed as a weighting of themeasured pressure vector as:

$\begin{matrix}{{{SPL\_ W}(n)(t)} = {20\;{\log\left( \frac{\Delta\;{P^{W_{A}}(t)}}{\Delta\; P_{0}} \right)}}} & (5)\end{matrix}$

where ΔP(t) is the measured temporal change in root mean squaredpressure, which can be converted into spectral space (e.g., FFT) asΔP(f) which is the measured spectral change in pressure, which can inturn be multiplied by a weighting function (e.g., A-weighting),W_(A)(f)) and expressed as ΔP^(W) ^(A) (η)=ΔP(ƒ)·W_(A)(ƒ)−, and thenreconverted (e.g., inverse FFT) into temporal space to obtain ΔP^(W)^(A) (t). To obtain a single value various integration or summation overthe n-th time interval (e.g., which can change in time) can beperformed. For example:

$\begin{matrix}{{{SPL\_ W}(n)} = {\frac{1}{\Delta\; t_{n}}{\int_{t_{n - 1}}^{t_{n}}{10\;{\log\left( \frac{\left( {\Delta\;{P^{W_{A}}(t)}} \right)^{2}}{\Delta\; P_{0}^{2}} \right)}\ {\mathbb{d}t}}}}} & (6)\end{matrix}$

The time during which a user may be exposed to the sound level SPL_W(n),i.e. the time to 100% allowable dosage at SPL level SPL_W(n), isreferred to below as Time_100%(n).

The weighting curves can be stored as a lookup table on computer memory,or can be calculated algorithmically. Alternatively, the input audiosignal can be filtered with a time or frequency domain filter utilizingthe weighting curve stored in step 412 and the sound pressure level ascalculated. For low-level sound pressure levels, those less than 50 dB,by way of non-limiting example, a weighting curve, which attenuates lowand high frequencies can be applied (similar to an A-weighting curve).For higher sound pressure levels, such as more than 80 dB, by way ofnon-limiting example, the weighting curve can be substantially flat or aC-weighting curve. The resulting weighted ear canal sound pressure levelduring any respective sampling epoch is returned as the system outputSPL_W(n) in step 414. Note that herein various conventional weightingschemes are discussed (e.g., A-weighting, C-weighting) however in atleast one exemplary embodiment non-conventional weighting schemes can beused. For example, generally the threshold level of hearing sensitivity(threshold of detection) is referenced in dB, where 20 micropascals istypically used as the minimum threshold level of pressure variation thatan average normal-hearing person can detect. This reference value tendsto be used at all frequencies, although the threshold level varies withfrequency. Thus, one weighting scheme is to adjust the reference 0 dBlevel on a frequency basis, by using a conventional dB of thresholdhearing chart, which provides the dB (f) at threshold level. A weightingfunction can be used where the value is about 1 at the reference value(e.g., equivalent to 20 micropascals) at a reference frequency (e.g.,1000 Hz). The other values (e.g., as a function of frequency) of theweighting function can vary depending upon the reference thresholdpressure variation for the particular frequency, for example if at 30 Hzthe threshold level in dB is 65 dB, then the weighting value can be 1/65at 30 Hz, de-emphasizing the loudness and/or intensity at 65 dB whenSPL_Dose (f) is calculated.

Returning to FIG. 3, a safe listening time is calculated by comparingthe weighted sound pressure level with the PSL (e.g., effective quietlevel) in step 316. Therefore, a value A corresponding to how far fromsafe listening the sound pressure level is, is determined by theequation:A=SPL_W(n)−PSL  (7)where PSL is the permissible sound level, for example PSL=EfQ, where EfQis equal to the sound level of effective quiet (as stored at step 312).However, PSL can be any level chosen for the particular circumstance,for example lower than EfQ.

By utilizing this simple comparative function, fewer machinations andprocesses are needed. System 100 takes advantage of the fact thatbecause the PSL (e.g., effective quiet level) can be neutral to the ear,sound pressure levels significantly above the PSL (e.g., effective quietlevel) are generally damaging and noise levels below the PSL (e.g.,effective quiet) generally allow for restoration/recovery.

In step 318, the remaining safe listening time at the beginning of anycurrent sampling epoch can be calculated by Time_100% minus the timeduration of exposure up to the current sampling epoch. Note that anegative number can occur, indicating that no safe listening timeremains. The estimated time (e.g., in hours) until the individual'ssound exposure is such that permanent threshold shift may occur,ignoring any previous sound exposure and assuming that the SPL of thesound field exposed to individual remains at a constant level L can becalculated as follows:Time_100%(n)=T _(c)/(2^((SPL_W(n)−PSL)/ER));  (8)

Where PSL is the permissible sound level, and Tc is the critical timeperiod. For example, if Tc (Critical Time) is 8 hours and PSL is 90 dBAand ER (the Exchange Rate) is 5 dB, then that accepts that ˜22-29% ofpeople are at risk for hearing loss. If Tc is 8 hours and PSL is 85 dBAand ER is 3 dB, then that accepts that ˜7-15% of people are at risk,likewise for if Tc is 24 hours and PSL is 80 dBA and ER is 3 dB, same7-15% at risk. Thus Time_100%(n) reflects a reduction of the risk to achosen level. Note that T_(c) is the critical time period of exposurethat one is looking at (e.g., 8 hours, 24 hours), and ER is the exchangerate, for example can be expressed as:Time_100%(n)=8(hours)/(2^((SPL_W(n)−85 dBA)/3 dB))  (9)

These values assume a recovery period of 16 hours at a SPL during thattime of less than 75 dBA (where dBA refers to Decibels of an A-weightedvalue). Of course the realism of such an assumption is questionablegiven music, TV, and other listening habits of individuals. Thus, we areconcerned with exposure over a 24-hour period. Thus, Time_100%(n) can beexpressed for a 24 hour period (e.g., T_(c)=24 (hours)), where, forexample using an equal energy assumption (i.e., ER of 3 dBA), as:Time_100%(n)=24/(2^((SPL_W(n)−PSL)/3)).  (10)

Another further example is the situation where PSL=EfQ, where theEffective Quiet, EfQ is defined as the highest sound level that does notcause temporary or permanent hearing threshold shift, nor does it impederecovery from temporary hearing threshold shift. For broadband noise, itcan be 76-78 dBA, although these numbers can be different or refinedover time based upon research and/or measurement history.

As a non-limiting example, the lower bound of SPL_W(n) dictating theTime_100% equation would be SPL_W(n)=PSL, and the upper bound of theSPL_W(n) dictating Time_100% equation would be about SPL_W(n)=115 dB.

Note that in at least one exemplary embodiment, the acoustic signalsmeasured by an ECM or an ECR in ECM mode, can be used to detect a user'svoice, for example using the technology discussed in Webster et al.,U.S. Pat. No. 5,430,826, incorporated by reference in its entirety. Ifvoice is detected then by the magnitude of the SPL (e.g., 80 dB) one cantell whether the user is speaking as compared to a non-user's voice(e.g., 50 dB) that has been attenuated by the earpiece. When a user'svoice is detected then SPL_W(n) can be reduced by an amount (DSPL, e.g.,20 dB) that is due to Stapedius (Middle-ear Muscle) Reflex (e.g., whenthe user's voice triggers a muscle response in the muscles supportingthe ossicles transmitting sound from the eardrum to cochlea),effectively damping some of the sound. ThusSPL_W(n)_(new)=SPL_W(n)−DSPL, where SPL_W(n)_(new) is used in theTime_100% (n) equation as opposed to SPL_W(n).

In this embodiment, rather than make use of the Sound Level (L), theperiod is a function of the intensity (both high and low) of theweighted sound pressure level. It should be noted that PSL (e.g.,effective quiet) is used in the above example, but any level ofinterest, such as 80 dB, or no sound level, i.e., SPL_W(n)−0, can beused. The weighted sound pressure level and PSL can be expressed as afrequency-dependent numerical array or a value scalar.

It is next determined whether or not the difference between the currentweighted sound pressure level and the PSL (e.g., effective quiet) isabove a tolerable threshold for risk of hearing damage or not, i.e.,whether the weighted SPL in the eardrum is considered to increase riskfor hearing damage or not. A sound pressure level dose is calculateddepending upon whether the sound level is sufficiently intense or not.The sound pressure level dose (SPL_Dose) is the measurement, whichindicates an individual's cumulative exposure to sound pressure levelsover time. It accounts for exposure to direct inputs such as MP3players, phones, radios and other acoustic electronic devices, as wellas exposure to environmental or background noise, also referred to asambient noise. The SPL_Dose is expressed as a percentage of some maximumtime-weighted average for sound pressure level exposure.

Because the sound pressure level dose is cumulative, there is no fixedtime-period for ear fatigue or damage. At or below effective quiet, thesound pressure level exposure time would theoretically be infinite,while the time period for achieving the maximum allowable sound pressurelevel dose becomes smaller and smaller with exposure to increasinglymore intense sound. A tolerable level change threshold corresponding tothe amount of noise above or below the effective quiet, which has nogreat effect on the ear as compared to effective quiet, is determinedand stored in memory 127 in a step 320. In a step 322, the differentialbetween the weighted sound pressure level and the effective quiet iscompared to the level change threshold.

A differential value A, corresponding to the level change, can becalculated as follows:A=SPL_W(n)−PSL  (11)

If A is greater than the level change threshold, the noise is consideredto increase risk for hearing damage and the sound pressure level dose iscalculated in a step 324 as follows:SPL Dose(n)=SPL Dose(n−1)+(Update_Epoch(n)/Time_100%)  (12)where SPL Dose(n−1) is the SPL Dose calculated during the last epoch;Update_Epoch is the time (in hours) since the last SPL Dose wascalculated. As described above, Update_Epoch can be adaptive, e.g.,shortened when the sound pressure level is higher; and Time_100%(n), thetime period remaining for safe exposure is determined by the equation:Time_100%(n)=24 hours/(2^((L−PSL)/3))  (13)where L=sound level (in dB) of the combination of environmental noiseand audio playback. It should be noted that sound level (L) can besubstituted for SPL_W(n).

It should be noted, as can be seen from the equation, that the timevalue becomes more important than the sound pressure level as updatesare spread apart. However, this is to protect overexposure to harmfulsounds because a less accurate sample size must account for the unknown.The wider the periodicity, the less accurate determination of actualexposure. Infrequent updates of the SPL Dose assume a relativelyconstant sound level, ignoring transients (e.g. spikes) and interveningrestorative periods. Accordingly, sound pressure level and epochperiodicity are weighed against each other to protect the ear.

If in step 322 it is determined that the differential is not greaterthan the level change threshold, including negative values for A (whichare restorative values), then in step 326 it is determined whether ornot the differential, as determined in step 316, is less than the levelchange threshold in a step 322. If it is determined that thedifferential is not less than the level change threshold, then thereceived noise was the effective quiet level, i.e., the level changethreshold equals zero and in a step 330, the current SPL Dose ismaintained at the same level. There is no change to the dose level.However, if the differential A is less than the level change thresholdthen this is a restorative quiet as determined in step 326. Thus, if thedifferential A (e.g., A=SPL_W(n)−PSL) is less than zero, withinmeasurement error, then this is considered a restorative quiet, then then-th SPL dose is determined, at step 328, asSPL Dose(n)=SPL Dose(n−1)*e^(−Update_epoch/τ)  (14)where: τ (referred to as “tau” in the following diagrams) can vary(e.g., equal to about 7 hours). In some exemplary embodiments, tau isadaptive for different users. In at least one exemplary embodiment, thelevel change threshold (e.g., measurement error) is set at substantially0.9-1.0 dB.

Note that other forms of a recovery function can be used and thedescription herein is not intended to limit the recover function to anexponential relationship. For example, during lower exposure times(e.g., 102 minutes) some SPL values (e.g., 95 dB) can be used, if thesubsequent SPL is less than PSL, in a linear manner (for examplelinearly decreasing until there is a near zero threshold shift at 4000Hz after one day from the time at which SPL<PSL).

Another non-limiting example of a recovery function can be a combinationover certain exposure and decay periods (e.g., 7 day exposure at 90 dB,with an initial threshold shift after the 7 days of about 50 dB at 4000Hz). For example a slow decaying linear relationship can be applied forthe first few hours (e.g., 2 hours) where SPL<PSL, then an exponentialdecay from after the first few hours to a few days (e.g., 4 days) afterwhich a leveling trend can occur.

Additionally although a fractional increase in SPL Dose is given as anon-limiting example, SPL Dose increase can be linear or exponentialdepending upon the exposure SPL level and the duration. For example thegrowth can be linear at a certain SPL values (e.g., 95 dB) duringdifferent ranges of exposure time (e.g., for 95 dB, from about 4 minutesto 12 hours), then leveling out (e.g., threshold shift of about 59.5 dB)when the exposure time exceeds a certain length (e.g., for 95 dB about12 hours).

In at least one exemplary embodiment the SPL values measured by an ECM(e.g., in an ECM mode) can be modified by a modification value (e.g.,additive or multiplicative), for example SPL_(new)=βSPL_(old)+δ, wherethe values, β and δ, can be time variant, positive or negative.Alternatively the values can be applied to the measured pressure valuesin a similar manner. One can convert the SPL measured by an ECM to freefield values, which then can be compared to free field standards fordamage risk criteria. For example Table 1 lists several frequencydependent responses of an earpiece while inserted, the “A” weightingcurve offset, and the modification values β and δ.

TABLE 1 Earpiece “A” weight Freq. Freq. Resp. offset β δ (Hz) (dBSPL/V)(dB) (dB) (dB) 100 95 −19.1 1.0 0.00 500 103.5 −3.2 1.0 −0.13 1000 104.00.0 1.0 −1.83 2000 121.0 1.2 1.0 −7.84 4000 106.0 1.0 1.0 −15.57

Thus, for example an SPL (f) measured at 80 dB, at f=1000 Hz, would besubtracted by −1.83 to obtain a free field value to compare withdamage-risk criteria, thus obtaining an SPL_(new) of 78.13 dB. Note whatis described is a non-limiting example, various other earpieces can havedifferent values, and the SPL_DOSE equations, described herein, (e.g.,SPL_Dose(n), Time_100%) can be based upon SPL_(new). Note that furtherdiscussions concerning frequency responses and free field estimate (FFE)conversion can be viewed in U.S. Pat. No. 6,826,515, Bernardi et al.Alternatively ear canal dBA SPL (e.g., as measured by an ECM) may beconverted to FFE dBA SPL using Table 1 of ISO 11904-1 (2002),incorporated herein by reference.

In step 332, the recovery time constant tau is determined. It may not bea function of exposure, but rather of recovery. It can be a defaultnumber or be determined as will be discussed below. As the SPL Dose iscalculated by system 100, it is also monitored. Once the SPL Dosereaches a certain level, as it is a cumulative calculation, ear fatiguecalculator 130 determines whether or not the SPL Dose corresponds to afatigued ear, and if so, it outputs warnings as discussed in connectionwith FIG. 1.

Reference is now made to FIG. 5 which depicts an optional methodologyfor not only updating the recovery time constant (tau) for individualusers, but to provide additional methods for acting upon detecteddamaging exposure. The process is started at a step 548. In a step 550,it is determined whether or not the user wishes to make use of aregistration process, for example online, for setting a personalizedupdate epoch through communication with a remote registration system. Ifthe user declines the registration, then the default tau is set at 7hours in a step 552. In a step 554, this default value is transmitted tosystem 100 via a wired or wireless data communication network.

Alternatively, if the user registers in step 550, a questionnaire ispresented in a step 556 in which the user informs system 100 regarding auser sound exposure history, age, work habits and other personal detailsthat could affect the user's personal recovery function time, i.e., thetime constant tau. The individual characteristics can be input to aformula or utilized as part of a look up table to determine the tau forthe individual user. The estimate of tau determined in step 556 istransmitted to system 100 via a wireless or wired data communicationsystem in a step 558. In step 560, the initial estimate of tau is setfrom the value determined in step 556 (or step 552).

An initial hearing test is performed in a step 561, which acquires dataindicative of the user's hearing sensitivity and/or auditory function.The test may be an otoacoustic emission (OAE) test or audiogramadministered utilizing the ear canal receiver or speaker 25. However,the test can also be administered over the Internet, telephone or othercommunication device capable of outputting sounds sent across adistributed network and enabling responsive communication. The data isstored in a computer memory as an initial test value in a step 570 andis used in further processing to detect a change in the user hearingresponse.

In a step 564, it is determined whether the user has been recentlyexposed to intense sound pressure levels. This can be done utilizing thesound pressure level dose as stored or permanently calculated by system100. If it is decided in step 564 that the user's ear canal soundpressure level is low, then in a step 559 it is determined whether thetime since the last test is greater than a maximum test epoch. At theoutset, the maximum test epoch is a set number determined in a step 562.In this non-limiting example, the maximum test epoch is set at 20 hours.

If it is determined that the time since the last test is greater thanthe maximum test epoch or, that there has been recent exposure tointense sound pressure level, then another test is administered in astep 566. The resulting test metrics are stored in steps 568, 570. In astep 571, the newly determined test metrics are compared to the initialtest metrics to calculate any change in the metrics. In step 572, it isdetermined whether the change is predictive of hearing damage. If not,then in a step 582, the tau is modified according the obtained metric.

If it is determined that hearing damage is predicted, then in a step 578the user is recommended to remove themselves from the noise as discussedabove with the operation of listening fatigue calculator 130 andfurthermore, the user can be recommended to seek professionalaudiological evaluation in a step 578. This could be done by an in situauditory or visual warning in step 580 by system 100. On the other hand,if system 100 is used in connection with a communications device such asa telephone or a personal digital assistant, an e-mail can be created insteps 574, 576; not only warning the user of potential damage, butnotifying a health professional so that a follow up examination can beperformed.

It should be noted that a change in the hearing metric (e.g., a hearingsensitivity curve) is measured by system 100. In response to the user'shearing metric, the recovery time constant tau is updated. For example,tau is lengthened if the change in the user's hearing metric indicatesthe user has “sensitive ears”, i.e., if, following intense soundexposure, the user's hearing sensitivity takes longer than theexponential function with time-constant of seven hours to return to theindividual's normal. This modified tau can be used to calculate thesound pressure level dose, in particular in a restorative phase, todetermine a better overall effect of sound pressure level exposure.

By providing a monitoring and protective system which, in at least onemode, continuously monitors sound pressure level at the ear until apotentially harmful exposure has occurred, rather than only monitoringfor a predetermined time as with noise dose monitors which monitor forwork shifts, a more accurate predictor of harm to the ear is provided.By utilizing a method, which determines exposure in part as a functionof effective quiet exposure as well as intense noise exposure, anenhanced model of potential risk is achieved. By providing a series ofwarning mechanisms and preventive measures as a function of thedetermined potentially harmful dosage levels ear damage is more likelyto be prevented. By providing the system in an earpiece whichsubstantially occludes the ear and making use of audio inputs at thelateral and medial portions of the ear canal (particularly with anoccluding device between lateral and medial portions of the ear canal),a more accurate reading of noise level is provided and more controlthrough a real time warning system is achievable.

It should be known that values for level change threshold, effectivequiet time, and epoch were used above as examples. However, it should benoted that any values which when input and utilized in accordance withthe methodologies above prevent permanent damage to the ear are withinthe scope of the invention and the invention should not be so limited tothe specific examples above.

Further Exemplary Embodiments

FIG. 8 illustrates the general configuration and some terminology inaccordance with descriptions of exemplary embodiments. An earpiece 800can be inserted into an ear canal separating the ambient environment(AE) 890 from an inner ear canal (IEC) 880 region, where a portion ofthe earpiece 800 touches a part of the ear canal wall (ECW) 870. Theearpiece 800 can be designed to vary its distance from the eardrum (ED)860. The earpiece 800 can have various elements, and the non-limitingexample illustrated in FIG. 8, can include three sound producing orreceiving elements coupled to input/output 840: an ambient soundmicrophone (ASM) 830 configured to sample the AE 890; an ear canalmicrophone (ECM) 820 configured to sample the IEC 880; and an ear canalreceiver (ECR) 810 configured to acoustically emit into the IEC 880.

FIGS. 9A-9C illustrates an example of a temporal acoustic signal and itsconversion into a spectral acoustic signature. FIG. 9A illustrates atemporal acoustic signal (AS) 900 on a generic X-Y coordinate system(e.g., Y can be amplitude in dB, and X can be time in sec). A section910 of the AS 900 can be selected for further processing (e.g., forapplying filtering treatments such as a FFT). For the non-limitingexample of using a Fast Fourier Transform (FFT) on section 910, a window920 can be applied to the section 910 to zero the ends of the data,creating a windowed acoustic signal (WAS) 930. An FFT can then beapplied 940 to the WAS 930 to generate a spectral acoustic signal (SAS)950, which is illustrated in FIG. 9C, where the Y-axis is a parameter(e.g., normalized power) and the X-axis is frequency (e.g., in Hz).

FIG. 10 illustrates a generalized version of an earpiece 800 and someassociated parts (e.g., ASM 830, ECM 820, and ECR 810) in an ear canal.When inserted the earpiece 800 generally defines the two regions 890 and880. Through the earpiece 800 there is some attenuation. For example, anambient acoustic signal (AAS) 1010A, will travel through the earpiece800 and/or via bone conduction (not shown) and be attenuated forming anattenuated ambient acoustic signal (AAAS) 1010B. The AAAS 1010B thentravels to the ED 860. The other additional acoustic signal 1010C (e.g.,the ECR generated AS or ECRAS), which can travel to the eardrum 860, canbe generated by the ECR 810. Thus the total AS imparting energy upon theED 860 can be due to the AAAS 1010B (which can include a bone conductionpart not in the IEC 880) and the ECRAS 1010C. Various exemplaryembodiments can calculate SPL Dose due to the total imparting AS uponthe ED 860, using various combinations of elements (e.g., parts) such asthe ECR 810 (e.g., Knowles FG3629), the ECM 820 (e.g., Knowles FK3451),and the ASM 830 (e.g., Knowles FG3629). Note that ECM 820 can alsomeasure head attenuated acoustic signals (HAAS) 1010D, which for examplecould originate from voice.

During operation, a personal audio device outputs a driving signal toECR 810 so that ECR 810 outputs an acoustic signal 1010C. Similarly, ASM830 converts the ambient environment noise into an environmental noisesignal, which is input to ECR 810 to generate an ECR ambient soundacoustic signal, which could make up a part of acoustic signal 1010C.ECM 820 receives an ambient acoustic signal AAS1010B and theECR-generated signal 1010C and converts it into a total acoustic soundsignal to be operated on by earpiece 800 as discussed below.

FIG. 11 illustrates an earpiece 1100 according to at least one exemplaryembodiment including an ECR 810 and an ECM 820. ECRAS 1010C generated bythe ECR 810 can be predicted and used to predict an equivalent SPL Doseas discussed later. Note that additional elements (e.g., logiccircuit(s) (LC), power source(s) (PS), can additionally be included inthe earpiece 1100). For example FIG. 12 illustrates a self-containedversion of an earpiece 1200 according to at least one exemplaryembodiment, including a power source (PS) 1210 (e.g., zinc-air battery(ZeniPower A675P), Li-ion battery), and a logic circuit (LC, e.g.,Gennum Chip GA3280) 1220 in addition to ECR 810. Earpiece 1200 can alsoinclude a wireless module for wireless communications (not shown) or canbe wired. Earpiece 1200 can also connect remotely to various parts(e.g., via a wired or wireless connection). For example FIG. 13illustrates an earpiece 1300 where parts are not contained in theearpiece directly according to at least one exemplary embodiment. Asillustrated the LC 1220 and PS 1210 are operatively connected (OC) 1310(e.g., via a wire or wirelessly) to the earpiece 1300. For exampleearpiece 1300 can be an earbud that includes ECR 810, whose signalstravel back and forth via a wire that is operatively connected via awire to LC 1220, which in turn can be operatively connected to PS 1210.Note that ECR 810 can also be a dual purpose ECR/ECM, where when thereceiver function (ECR mode) is not used the microphone function (ECMmode) can be used. For example U.S. Pat. No. 3,987,245 discusses adual-purpose transducer that can be used as a microphone and/or areceiver.

FIG. 14A illustrates a general configuration of some elements of anearpiece according to at least one exemplary embodiment. Again, likenumerals are utilized to indicate like structure in which an earpiece1400 includes a logic circuit 1220. Logic circuit 1220 has an operativeconnection 1310A to ASM 830; operative connection 1310B to a memory1420; operative connection 1310C to ECR 810; operative connection 1310Dto ECM 820; operative connection (e.g., operatively connected) 1310E toa communication module 1410; and an operative connection 1310F to apower source 1210. Again, it should be noted that the operativeconnection could be either wireless or hard wired and that as discussedabove, elements other than ECR 810 could be remote from earpiece 1400.It should be understood that ASM 830 cannot be too remote from the earof the user in order to properly measure the ambient sound and ambientenvironment 890.

ECM 820 measures the noise level as it exists in inner ear canal 880.This includes ambient sound as attenuated by earpiece 800 and/or anysound produced by ECR 810 from an associated Personal Acoustic Device orfrom ASM 830. FIG. 14B illustrates a flow diagram of a method forSPL_Dose calculation and response according to at least the exemplaryembodiments of earpieces 1100-1300; i.e., using only ECM 820. Logiccircuit 1220 and the other elements are powered by power source 1210.Logic circuit 1220 processes signals as received from ECM 820. Logiccircuit 1220 may make use of controls, weighting curves, and storedvalues as discussed above, in order to process the acoustic signalsdetected by ECM 820.

Total SPL_Dose is a function of both ambient noise and any drivingsignals delivered to ECR 810 or ECM 820 from a connected personal audiodevice such as a cell phone or music player. Therefore, in accordancewith the invention, in a first step 1450A, the detected acoustic signaldetected in inner ear canal 880 is measured for a time period ΔT.

In a step 1450B, an SPL_Dose equivalent is calculated for the timeperiod Δt in accordance with any of the exemplary methods discussedherein. In a step 1450C, the SPL_Dose for the time period is added to,or subtracted from, the current Total SPL_Dose to obtain a new TotalSPL_Dose. In this way the total is continuously updated and monitored.It is understood that if the SPL_Dose for the time period is arestorative dose, then the effect during the time period Δt is negativerelative to damage and therefore is subtracted from the Total SPL_Doseat time t to obtain the new Total SPL_Dose. Conversely, if thecalculated exposure during the time period is greater than a permissiblesound level (PSL), the SPL_Dose for the current time period Δt isconsidered potentially damaging and will be added to Total SPL_Dose.

In a step 1450D, it is determined whether or not the Total SPL_Dose isgreater than a threshold value. If the Total SPL_Dose has not increasedto more than a threshold value, then the process is repeated in step1450A. If the Total SPL_Dose is greater than the threshold value thenlogic circuit 1220 checks for action parameters to be taken in a step1450E. An action parameter corresponds to the corrective action to betaken.

In a step 1450F, the action parameter could correspond to sending anotification signal such as an audio signal, output by ECR 810, ECM 820,or a visual notification on the associated personal audio device.Alternatively, the action parameter could correspond to modifying theaudio content through attenuation in a step 1450G as discussed above.Furthermore, the action parameter could correspond to modifying theoperation of the personal audio device itself in a step 1450H in whichthe device either shuts off or attenuates its output signal at itsorigination rather than attenuating the output signal at ECR 810 or ECM820 as in step 1450G. Other actions may be taken like those suggestedabove or others in a step 1450I.

It is well within the scope of the invention to modify the earpiecedevice in which the ECR 810 or ECM 820 may be utilized to function inboth capacities. In other words, the ECM 820 may be used to calibratethe ECR 810, to receive driving signals to function as an ECR in anembodiment in which both the ECR 810 and ECM 820 are simple transducers.

Additionally, ECM 820 may be utilized to detect the user's own voice asit is perceived within inner ear canal 880. Logic circuit 1220distinguishes between the user's own voice and the voices of others bydetermining a difference in the relative intensity of the voicesmeasured by ECM 820. Intensity is a function of the measured SPL_Dose.Therefore, by calculating relative SPL_Dose at ECM 820, logic circuitcan differentiate between and account for the voice of the user.

In one non-limiting example, ECM 820 measures acoustic signals below acertain threshold such as 40-50 dB. This is most likely, in oneembodiment, lower than the received speaking voice SPL of the user ofearpiece 800 at ECM 820. Therefore, logic circuit 1220 determines thatvoice frequencies at SPL levels below this threshold are not thespeaking voice of the user. Of course, the predetermined threshold levelcan be tuned from user to user depending upon their range of speakingvoice from whisper to shout.

In another embodiment, ASM 830 can also measure the voice of the user asa part of ambient environment 890 and compare that value to the SPL ofthe voice of the user as measured in the inner ear at ECM 820. TheSPL_Dose measured attributable to the user's voice within the inner earshould be greater than the value of the voice as part of the ambientenvironment 890. Therefore, logic circuit 1220 determines whether theECM SPL_Dose is greater than the ASM SPL_Dose to determine whether ornot words received belong to the user or a third party.

An Example of Calculating SPL

SPL exposure within the ear canal in accordance with the invention is afunction of noise from both the ambient environment and generated withinthe ear canal by ECR 810 as a function of input signals thereto. Anaccurate way to measure SPL exposure is to actually measure the noiselevel in inner ear canal 880. Accordingly estimated SPL_Dose may becalculated in one embodiment as follows:SPL_Dose_(ECM+ASM)=SPL_Dose_(ECM+ASM−1)+Time of Sound Exposure/Time100%  (15)where Time 100%=24 hrs/2^((L_(ECM+ASM)−80)/3)where L_(ECM+ASM) is the measured Ear Canal d/BA SPL by the ECM 820 andthe ambient SPL by the ASM 830. It is anticipated that the purpose ofthe ASM 830 will be to allow pick-up of environmental sound, but notnecessarily contribute to the determination of SPL_Dose in thisembodiment. Hence, L_(ECM+ASM) may be analogous to L_(ECM) alone. SoASK⁻¹ and ASM go to zero over time and only the ECM component need beaccounted for. Thus, the SPL_Dose can contain only measured componentsfrom the ECM 820. If for some reason the ECM 820 can not be used, abackup value of SPL measured by the ASM 830 corrected for NRR of theearpiece added to estimated SPL emitted by the ECR 810 can be used as aless accurate value of using the SPL value measured by the ECM 820. TheTime of Sound Exposure is the time during which L_(ECM+ASM) occurs.

The value of 80 in determining the time is a threshold value of interestfor decibels of the sound level in this one exemplary embodiment. Asdiscussed above, 80 does have some significance to audiologists, but thenumber may also be the effective quiet, or any other level predeterminedby a person skilled in the art designing the system as a function ofnoise exposure a user will be allowed to experience.

In at least one exemplary embodiment one can determine a Free FieldEquivalent (FFE) dBA SPL for purposes of determining pressure leveldose, the ear canal dBA SPL may be converted to FFE dBA SPL using Table1 of ISO 11904-1 (2002).

Exemplary embodiments of the present invention can be used in manyplatforms that direct and/or attenuate acoustic energy in the ear canal.FIGS. 15A to 15N illustrate various non-limiting examples of earpiecesthat can use methods according to at least one exemplary embodiment,when the various earpieces have an ECR 810 and an ASM 830.

FIG. 16 illustrates a line diagram of an earpiece 1600 (e.g., earbud)that can use methods according to at least one exemplary embodiment andFIG. 17 illustrates the earpiece 1700 of FIG. 16 fitted in an ear canal.Earbuds can be used with many devices such as audio playback devices,PDAs, phones, and other acoustic management devices. The software toimplement exemplary embodiments can reside in the earpiece (e.g.,hearing aid) or can reside in the acoustic management systems (e.g.,iPod™, Blackberry™, and other acoustic management devices as known byone of ordinary skill in the relevant arts).

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions of therelevant exemplary embodiments. For example, although specific numbersmay be quoted in the claims, it is intended that a number close to theone stated is also within the intended scope, i.e., any stated number(e.g., 80 dB) should be interpreted to be “about” the value of thestated number (e.g., about 80 dB). Thus, the description of theinvention is merely exemplary in nature and, thus, variations that donot depart from the gist of the invention are intended to be within thescope of the exemplary embodiments of the present invention. Suchvariations are not to be regarded as a departure from the spirit andscope of the present invention.

What is claimed is:
 1. A system configured to monitor a sound pressurelevel dose at an ear comprising: an ear canal microphone configured tomeasure a first acoustic sound pressure level (SPL1) within an ear canalof the ear; an ambient microphone configured to measure a second soundpressure level (SPL2); and a logic circuit operatively coupled to theear canal microphone, where the logic circuit is configured to:calculate a noise reduction rating (NRR) using the SPL1 and the SPL2;compare the NPR to a threshold value of the NRR; and send a signal toindicate a sealing integrity compromise if the NPR is less than thethreshold value of the NRR.
 2. The system of claim 1, wherein the logiccircuit calculates a Total SPL_Dose as a function of an estimatedSPL_Dose during a time period Δt.
 3. The system of claim 2, wherein theestimated SPL_Dose is calculated as:SPL_Dose_(ECM+ASM)=SPL_Dose_(ECM+ASM−1)+Time of Sound Exposure/Time100%, where Time 100%=24 hrs/2^((L_(ECM)−T)/3), where L_(ECM) is ameasured Ear Canal d/BA SPL by the ear canal microphone, and where T isa threshold value related to noise level.
 4. The system of claim 2,further comprising a readable memory operatively connected to the logiccircuit, at least one action parameter stored in the readable memory,the logic circuit comparing the Total SPL_Dose to a threshold value, andif the Total SPL_Dose is greater than the threshold value, then thelogic circuit reads the action parameter from the readable memory. 5.The system of claim 4, wherein the logic circuit performs an actionassociated with the action parameter, where the action is at least oneof modifying an operation of an audio device, modifying at least oneacoustic signal directed to an ear canal receiver (ECR), and sending anacoustic notification signal to a user.
 6. The system of claim 3,wherein the logic circuit determines whether the estimated Total SPLDose exceeds a minimum threshold and reduces the Total SPL_Dose byselection of an action parameter.
 7. The system of claim 6, wherein theminimum threshold is an effective quiet level.
 8. The system of claim 1,wherein the ambient sound microphone measures an ambient SPL.
 9. Thesystem of claim 1, wherein the logic circuit compares the SPL1, to athreshold value and determines whether the SPL1 corresponds to a voiceof a user of the system.
 10. The system of claim wherein the logiccircuit is configured to compare the SPL1 to the SPL2 and determinewhether the SPL1 includes an acoustic signal corresponding to a voice ofuser.
 11. The system of claim 1, wherein the logic circuit furtherestimates a third sound pressure level (SPL3) emitted by an ear canalreceiver (ECR.
 12. The system according to claim 11, wherein the logiccircuit further calculates the total sound pressure level (SPL_Total),using the SPL1 and at least one of the SPL2 or the SPL3.
 13. The systemaccording to claim 12, wherein the logic circuit further: calculates aTime_100% for a time increment Δt during which the SPL_Total occurs. 14.The system according to claim 13, wherein the logic circuit further:calculates a total sound pressure level dose (SPL_Dose total) using theTime_100%.
 15. The system according to claim 14, wherein the logiccircuit further: compares the SPL_Dose total to a threshold value and ifthe SPL_Dose total is greater than the threshold value, sending a signalto the user.
 16. The system according to claim 15, wherein the logiccircuit further: modifies a drive signal sent to the ECR so that a SPLemitted by the ECR is reduced if the SPL_Dose total is greater than thethreshold value.